The present invention relates to an oxygenator of hollow fiber membrane type for removing carbon dioxide contained in blood and adding oxygen to the blood in an extracorporeal blood circulation.
In recent years, there is proposed (for example, Japanese Patent Application Laid-Open No. 7-509171) an oxygenator using a hollow fiber membrane bundle produced by winding hollow fiber membranes spirally on a hollow cylindrical core. The hollow fiber membrane bundle of this type has cross portions where the wound hollow fiber membranes cross.
Cross Portions of the wound hollow fiber membranes and annular portions formed of the cross portions layered one on the other are formed by controlling a rotating means for rotating the hollow cylindrical core and a winder for weaving the hollow fiber membranes under a predetermined condition. A short circuit of blood may be formed due to the annular portions formed of the cross portions layered one on the other, which causes reduction of gas exchange performance.
Therefore, in providing an oxygenator of hollow fiber membrane type using a hollow fiber membrane bundle produced by winding hollow fiber membranes spirally on a hollow cylindrical core and having annular portions formed of cross portions of the hollow fiber membranes layered one on the other, the oxygenator is intended to hardly generate a cross portion-caused short-circuited path of blood and have a high degree of gas exchange performance.
The object of this invention is to provide an oxygenator of hollow fiber membrane type that comprises a cylindrical core; a cylindrical hollow fiber membrane bundle consisting of a plurality of gas-exchange hollow fiber membranes wound on an outer surface of said cylindrical core; a housing accommodating said cylindrical hollow fiber membrane bundle; a gas inlet portion and a gas outlet portion both communicating with the interior of said hollow fiber membranes; and a blood inlet portion and a blood outlet portion communicating with the outside of said hollow fiber membranes and the interior of said housing, wherein said hollow fiber membranes of said cylindrical hollow fiber membrane bundle are multi- layered on the outer surface of said cylindrical core; each hollow fiber membrane layer has cross portions of the hollow fiber membranes in the neighborhood of a center of said cylindrical core in the longitudinal direction thereof and positions of said cross portions of each of said respective hollow fiber membrane layers are differentiated from one another to prevent contact between said cross portions of said hollow fiber membrane layers laminated on each other or to prevent contact between said cross portion of another hollow fiber membrane layer and cross portions of two hollow fiber membrane layers laminated on each other.